1. Field of the Invention
The present invention relates to a multi-compartment tube mill for the grinding of coarse material.
2. Description of the Prior Art
It is well known in the prior art to use multi-compartment mills for grinding coarse material and for effecting an exchange of heat with air or gas. Such mills have generally included an inlet at one end of the material to be ground and for entry of the air or gas, and an outlet at the other end for exiting the ground product and the air or gas which has participated in a heat exchange process in the mill. At the same time the air or gas usually serves as a transport medium for carrying the ground product out of the mill to a separator. The mills generally include a separator which may be in the form of a common cyclone or an air classifier from which the oversize material is usually returned to the mill for further grinding.
It is also known to use multi-compartment mills having a central discharge chamber from which material is discharged together with the air or the gas, through peripheral openings in the mill shell; whereas, depending on the process performed in the mill, raw material and/or coarse material is fed to both ends of the mill together with air or gas.
In multi-compartment mills of the last mentioned type, it is also known to process material for grinding and drying by directing hot gas together with moist material to one end of the mill and by introducing additional hot gas into the central discharge chamber for passing countercurrently to the material fed to the inlet end of the mill which is flowing from that feed end to the central discharge chamber.
In these known constructions it is difficult to achieve the desired heat exchange, especially in mills adapted for large production. Such large production mills generally combine the cross-section of the mill with a preferred low velocity of the air or gas to restrict the amount of air or gas passing therethrough. Further, the constructions having a central outlet generally involve complicated installations with feed arrangements at both ends of the mills and conveyors for transporting and distributing the ground and the classified material.
The known mills of this type are particularly not suitable for carrying out a controlled grinding and heat exchange process especially when grinding heat-sensitive material such as cement clinker. I have invented an improved multi-compartment tube mill in which these disadvantages are avoided.